A hollow structural section (HSS) is a steel tube with a square, rectangular or round cross-section that is hollow on the inside. HSS members are strong for their weight in compression and torsion, so they are widely used for columns, braces, posts, canopies and exposed structural steel.
You’ll also hear hollow steel section, tube steel (TS, the older North American name), and in the UK and Australia SHS, RHS and CHS for square, rectangular and circular hollow sections.
How HSS sizes are written
- Square and rectangular (US): outside dimensions and wall thickness in inches, for example HSS8x8x1/2 or HSS6x4x3/8.
- Round (US): outside diameter and wall thickness, for example HSS6.625×0.280.
- Canada: the same pattern in millimetres, for example HSS 152x152x9.5.
- UK/Europe: SHS 100x100x6.3 style, in millimetres.
Material specifications
- ASTM A500: the common US spec for cold-formed HSS. Grade C (50 ksi yield for square and rectangular) is now the usual grade.
- ASTM A1085: tighter tolerances and toughness requirements, used where those matter.
- Design wall thickness: AISC 360 designs A500 sections with 0.93 times the nominal wall, because the tolerance allows thinner walls. A1085 uses the full nominal thickness.
- Canada: CSA G40.21 350W, Class C (cold-formed) or Class H (stress-relieved).
- UK/Europe: EN 10210 (hot-finished) and EN 10219 (cold-formed), often S355.
For how forming method affects tubes, see our article on hot rolling vs cold rolling of square and rectangular tubes.
HSS vs W-shape vs pipe
| HSS | W-shape (wide flange) | Pipe | |
|---|---|---|---|
| Best at | Compression in both directions, torsion | Bending about one axis | Fluid service; some columns and bollards |
| Look | Clean, popular for exposed steel | Industrial | Round only |
| Connections | Harder: inside isn’t reachable, so welded tabs or through plates | Easy to bolt to flanges and web | Similar to round HSS |
| Spec (US) | A500, A1085 | A992 | A53 |
Where HSS is used
Columns in low and mid-rise buildings, braced frames, canopy and entrance framing, guardrail posts and handrails, lintels, trusses, sign and screen supports, mechanical frames, and architecturally exposed structural steel. HSS columns can also be filled with concrete to act compositely.
Detailing and site tips
- HSS to be hot-dip galvanized needs vent and drain holes, or trapped air and moisture can make it burst in the bath.
- Seal exterior HSS with cap plates, or detail drainage, so water can’t collect and freeze inside.
- Check that connection plates and through-bolts suit the wall thickness; thin walls can distort under concentrated loads.
- Exposed HSS often gets intumescent paint for fire protection.
Related terms
Related templates and guides
- Guide to the design and construction of structural steel
- ANSI/AISC 360-16 Specification for Structural Steel Buildings (since updated to 360-22)
- Design Guide 01: Column Base Plates and Anchor Design
- Design Guide 19: Fire Resistance of Structural Steel Framing
Frequently asked questions
What does HSS stand for in construction?
HSS stands for hollow structural section: a square, rectangular or round steel tube used as a structural member. It is often called tube steel on site, and SHS, RHS or CHS in the UK, Australia and Europe.
What does HSS 6x6x1/4 mean?
It is a square hollow structural section with 6 inch by 6 inch outside dimensions and a nominal 1/4 inch wall. Rectangular sizes list the larger side first, and round HSS list the outside diameter and wall thickness instead.
Is HSS the same as tube steel?
Yes. ‘Tube steel’ or ‘TS’ is the older North American name, and many people still use it. Drawings and specifications now generally use HSS, which matches AISC terminology and avoids confusion with mechanical tubing.
What is the difference between RHS and SHS?
RHS is a rectangular hollow section and SHS is a square hollow section. Both are hollow structural sections; the names come from UK and European usage. CHS is the circular version. In North America all three are simply called HSS.
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